A UNO can operate of an external supply of max 6 - 20 volts DC. My question is: can the same input be wired safely into an analog input.
For example if I'm solar charging a 12V battery can that same 12v supply be directly wired to power the UNO and also to an analog input so I can monitor / log battery voltage over time ?
Can a DC voltage above the power supply voltage be safely connected to analog input? Would the input just show full scale once it exceeds the power supply voltage ? Of course a simple resister voltage divider could be used.
rbright:
Can a DC voltage above the power supply voltage be safely connected to analog input? Would the input just show full scale once it exceeds the power supply voltage ?
No, unless you connect a series resistor between the voltage source and the analog input pin, with a high enough value that the current flowing into the pin protection diode never exceeds a few mA. Even then, any voltage over 5V will cause the analogRead to return 1023 (i.e. 5V).
rbright:
Of course a simple resister voltage divider could be used.
That's what you need to do to measure a voltage greater than 5V.
Does your solar panel produce stable 12V, or does it go higher? I would also like to monitor a solar panel (120W) and know that the raw voltage can go as high as 1000V (with ideal conditions) so I have to connect a solar regular to it, in order to charge the 12V battery but think the voltage can still spike upto about 14V.